On any observation detail page (e.g. https://www.inaturalist.org/observations/28034913), doing ctrl+click to open the observations listed in “More from @ user”, “Nearby observations”, or “Observations of relatives” at the bottom of the page does not open the observation in a new tab. It opens it in the same tab.
(Middle click and right click>open in a new tab do open it in a new tab.)
Windows 10 / Chrome and Firefox.